International Publication No. WO 2006/004957 describes a fuel cell. The fuel cell is provided with a silicon substrate, an electrolyte film laminated on the silicon substrate, and a gas flow path formed inside the silicon substrate. The electrolyte film is opposed to the gas flow path via an electrode film. An inclination angle of a side wall of the gas flow path with respect to the electrolyte film is substantially 55 degrees and is constant.